CN117525553A

CN117525553A - Lithium sulfur battery

Info

Publication number: CN117525553A
Application number: CN202310836688.6A
Authority: CN
Inventors: 李西濛; 金子咲南; 高木春树
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2022-08-03
Filing date: 2023-07-10
Publication date: 2024-02-06
Also published as: US20240047735A1; JP2024021430A

Abstract

The lithium-sulfur battery of the present disclosure includes a positive electrode, a 1 st electrolyte layer, a 2 nd electrolyte layer, and a negative electrode, the 1 st electrolyte layer is disposed between the positive electrode and the 2 nd electrolyte layer and is in contact with the positive electrode, the 2 nd electrolyte layer is disposed between the 1 st electrolyte layer and the negative electrode, the 1 st electrolyte layer includes a hydride solid electrolyte having lithium ions and complex ions containing hydrogen, and the 2 nd electrolyte layer includes an electrolyte different from the hydride solid electrolyte. The lithium sulfur battery of the present disclosure has a high capacity.

Description

Lithium sulfur battery

Technical Field

The application discloses a lithium sulfur battery.

Background

Japanese patent application laid-open No. 2021-515353 discloses an all-solid lithium battery having a positive electrode, a sulfide solid electrolyte layer, a borohydride solid electrolyte layer, and a negative electrode in this order. Japanese patent application laid-open No. 2022-01539 discloses a method for manufacturing a solid electrolyte layer using a slurry containing a borohydride compound and an alkane compound having 5 or 6 carbon atoms. On the other hand, as a battery having a high theoretical capacity, a lithium sulfur battery (LiS battery) is known.

Disclosure of Invention

Although a high capacity can be expected in theory in conventional lithium sulfur batteries, it is difficult to say that a sufficient capacity can be obtained in the present situation. There is room for improvement regarding the capacity of lithium sulfur batteries.

As means for solving the above problems, the present application discloses the following aspects.

Mode 1

A lithium sulfur battery comprising:

a positive electrode,

An electrolyte layer 1,

2 nd electrolyte layer

A negative electrode,

the 1 st electrolyte layer contains a hydride solid electrolyte having lithium ions and complex ions containing hydrogen, the 1 st electrolyte layer is disposed between the positive electrode and the 2 nd electrolyte layer and is in contact with the positive electrode,

the 2 nd electrolyte layer includes an electrolyte different from the hydride solid electrolyte, and is disposed between the 1 st electrolyte layer and the anode.

Mode 2

In the lithium sulfur battery of mode 1, the complex ion contains hydrogen, boron, and carbon.

Mode 3

In the lithium sulfur battery of mode 1 or 2, the surface area of the 1 st electrolyte layer on the 2 nd electrolyte layer side is larger than the surface area of the positive electrode on the 1 st electrolyte layer side.

Mode 4

In the lithium sulfur battery according to any one of aspects 1 to 3, at least a part of the side surface of the positive electrode is covered with the 1 st electrolyte layer.

Mode 5

The lithium sulfur battery according to any one of modes 1 to 4, wherein the 2 nd electrolyte layer comprises a sulfide solid electrolyte.

Mode 6

In the lithium-sulfur battery of mode 5, the sulfide solid electrolyte contains lithium, phosphorus, sulfur, and halogen.

The lithium sulfur battery of the present disclosure has a high capacity.

Drawings

Features, advantages, and technical and industrial significance of the exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings, in which like numerals represent like elements.

Fig. 1 schematically shows an example of the structure of a lithium-sulfur battery.

Fig. 2 schematically shows an example of the structure of a lithium-sulfur battery.

Fig. 3A schematically shows the structure of the 1 st transfer material obtained by the first step of the method for producing a lithium-sulfur battery.

Fig. 3B schematically shows the structure of the 2 nd transfer material obtained by the first step of the method for producing a lithium-sulfur battery.

Fig. 3C schematically illustrates a first step of the method for manufacturing a lithium-sulfur battery.

Fig. 3D schematically illustrates a first step of the method for manufacturing a lithium-sulfur battery.

Fig. 3E schematically illustrates a process of a method of manufacturing a lithium sulfur battery.

Detailed Description

1. Lithium sulfur battery

Hereinafter, the lithium sulfur battery of the present disclosure will be described with reference to the accompanying drawings. The lithium sulfur battery of the present disclosure is not limited to the illustrated form. Fig. 1 schematically shows the structure of a lithium-sulfur battery 100 according to an embodiment. The lithium-sulfur battery 100 has a positive electrode 10, a 1 st electrolyte layer 21, a 2 nd electrolyte layer 22, and a negative electrode 30. The 1 st electrolyte layer 21 is disposed between the positive electrode 10 and the 2 nd electrolyte layer 22, and is in contact with the positive electrode 10. The 2 nd electrolyte layer 22 is disposed between the 1 st electrolyte layer 21 and the negative electrode 30. The 1 st electrolyte layer 21 contains a hydride solid electrolyte containing Li ions and H-containing complex ions. The 2 nd electrolyte layer 22 contains an electrolyte different from the hydride solid electrolyte.

1.1 Positive electrode

The positive electrode 10 contains sulfur as a positive electrode active material. The positive electrode 10 may be any electrode that can function properly as a positive electrode of a lithium-sulfur battery. The structure thereof is not particularly limited. As shown in fig. 1, the positive electrode 10 may include a positive electrode active material layer 11 and a positive electrode current collector 12. In this case, the positive electrode active material layer 11 contains sulfur as a positive electrode active material.

1.1.1 Positive electrode active Material layer

The positive electrode active material layer 11 contains at least sulfur as a positive electrode active material, and may optionally contain an electrolyte, a conductive auxiliary agent, a binder, and the like. The positive electrode active material layer 11 may further contain other various additives. The content of each component in the positive electrode active material layer 11 may be appropriately determined according to the target battery performance. For example, the content of the positive electrode active material may be 10 mass% or more, 20 mass% or more, 30 mass% or more, 40 mass% or more, 50 mass% or more, 60 mass% or more, or 70 mass% or more, based on 100 mass% of the entire positive electrode active material layer 11 (solid content overall). The content of the positive electrode active material may be 100 mass% or less or 90 mass% or less. The shape of the positive electrode active material layer 11 is not particularly limited. The positive electrode active material layer 11 may be, for example, a sheet-like positive electrode active material layer having a substantially flat surface. The thickness of the positive electrode active material layer 11 is not particularly limited. The thickness of the positive electrode active material layer 11 may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more. The thickness of the positive electrode active material layer 11 may be 2mm or less, 1mm or less, or 500 μm or less.

As the positive electrode active material, at least sulfur is used as described above. Sulfur may function as the positive electrode active material. The sulfur may be elemental sulfur. Sulfur may also be a sulfur compound. The positive electrode active material layer 11 may contain a positive electrode active material other than elemental sulfur and a sulfur compound. Examples of the positive electrode active material other than elemental sulfur and sulfur compounds include various lithium-containing compounds. The lithium-containing compound may be lithium cobaltate, lithium nickelate, li _1±α Ni _1/3 Co _1/3 Mn _1/3 O _2±δ Lithium manganate, spinel-based lithium compound (Li _1+x Mn _2-x-y M _y O ₄ (M is an optionSubstitution of Li-Mn spinel or the like with a hetero element having a composition represented by one or more of Al, mg, co, fe, ni and Zn), lithium titanate, lithium metal phosphate (LiMPO) ₄ And M is at least one selected from Fe, mn, co and Ni). Further, the higher the proportion of sulfur in the entire positive electrode active material, the more likely the expansion and contraction of the positive electrode during charge and discharge become, and there is a concern that the electrolyte layer may crack. In contrast, in the lithium-sulfur battery 100, as will be described later, the 1 st electrolyte layer 21 contains a predetermined hydride solid electrolyte, and cracks in the electrolyte layer are easily suppressed. In this regard, in the lithium-sulfur battery 100, the proportion of elemental sulfur and sulfur compounds in the entire positive electrode active material contained in the positive electrode active material layer 11 may be high. Specifically, the ratio of elemental sulfur and sulfur compounds in the entire positive electrode active material contained in the positive electrode active material layer 11 may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or 90% by mass or more and 100% by mass or less.

The shape of the positive electrode active material may be any shape that is general as a positive electrode active material of a lithium-sulfur battery. The positive electrode active material may be, for example, granular. The positive electrode active material may be solid, hollow, porous, or porous. The positive electrode active material may be primary particles. The positive electrode active material may be a secondary particle in which a plurality of primary particles are aggregated. Average particle diameter D of positive electrode active material ₅₀ For example, the wavelength may be 1nm or more, 5nm or more, or 10nm or more. Average particle diameter D of positive electrode active material ₅₀ Can be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Further, the average particle diameter D as referred to herein ₅₀ The particle diameter (median diameter) is 50% of the cumulative value in the volume-based particle size distribution obtained by the laser diffraction/scattering method.

The electrolyte that may be contained in the positive electrode active material layer 11 may be a solid electrolyte or a liquid electrolyte (electrolyte solution). The electrolyte that may be contained in the positive electrode active material layer 11 may be a combination of these. In particular, when the positive electrode active material layer 11 contains at least a solid electrolyte as the electrolyte, a higher effect is easily obtained.

As the solid electrolyte, a substance known as a solid electrolyte of a battery can be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the inorganic solid electrolyte has high ionic conductivity and excellent heat resistance. Examples of the inorganic solid electrolyte include lithium lanthanum zirconate, liPON, and Li _1+X Al _X Ge _2-X (PO ₄ ) ₃ Oxide solid electrolytes such as Li-SiO glass and Li-Al-S-O glass; p (P) ₂ S ₅ 、Li ₂ S-P ₂ S ₅ 、Li ₂ S-SiS ₂ 、LiI-Li ₂ S-SiS ₂ 、LiI-Si ₂ S-P ₂ S ₅ 、Li ₂ S-P ₂ S ₅ -LiI-LiBr、LiI-Li ₂ S-P ₂ S ₅ 、LiI-Li ₂ S-P ₂ O ₅ 、LiI-Li ₃ PO ₄ -P ₂ S ₅ 、Li ₂ S-P ₂ S ₅ -GeS ₂ And sulfide solid electrolytes. In particular, sulfide solid electrolytes, which contain at least P and S as constituent elements, are high in performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be, for example, granular. The solid electrolyte may be used alone in an amount of 1 or in an amount of 2 or more.

The electrolyte may contain lithium ions. The electrolyte may be, for example, a nonaqueous electrolyte. The composition of the electrolyte may be the same as that known as the electrolyte of the battery. For example, as the electrolyte solution, an electrolyte solution in which a lithium salt is dissolved in a carbonate-based solvent at a predetermined concentration can be used. Examples of the carbonate-based solvent include fluoroethylene carbonate (FEC), ethylene Carbonate (EC), and dimethyl carbonate (DMC). Examples of the lithium salt include LiPF ₆ Etc.

Examples of the conductive auxiliary agent that can be contained in the positive electrode active material layer 11 include carbon materials such as vapor-phase carbon fiber (VGCF), acetylene Black (AB), ketjen Black (KB), carbon Nanotubes (CNT), and Carbon Nanofibers (CNF); nickel, aluminum, stainless steel, and the like. The conductive aid may be, for example, granular or fibrous. The size thereof is not particularly limited. The conductive auxiliary agent may be used alone in an amount of only 1. The conductive auxiliary may be used in combination of 2 or more.

Examples of the binder that can be contained in the positive electrode active material layer 11 include Butadiene Rubber (BR) -based binders, butyl rubber (IIR) -based binders, acrylate Butadiene Rubber (ABR) -based binders, styrene Butadiene Rubber (SBR) -based binders, polyvinylidene fluoride (PVdF) -based binders, polytetrafluoroethylene (PTFE) -based binders, polyimide (PI) -based binders, and the like. The binder may be used alone in an amount of only 1. The binder may be used in combination of 2 or more kinds.

1.1.2 Positive electrode collector

As shown in fig. 1, the positive electrode 10 may include a positive electrode current collector 12 in contact with the positive electrode active material layer 11. As the positive electrode collector 12, any current collector that is general as a positive electrode collector of a lithium-sulfur battery can be used. The positive electrode current collector 12 may be foil, plate, mesh, perforated metal, foam, or the like. The positive electrode current collector 12 may be made of a metal foil or a metal mesh. Particularly, the metal foil is excellent in handleability and the like. The positive electrode current collector 12 may be composed of a plurality of foils. Examples of the metal constituting the positive electrode current collector 12 include Cu, ni, cr, au, pt, ag, al, fe, ti, zn, co and stainless steel. In particular, from the viewpoint of securing oxidation resistance, the positive electrode current collector 12 may contain Al. The positive electrode current collector 12 may have a coating of some kind on its surface for the purpose of adjusting resistance or the like. The positive electrode current collector 12 may be a current collector obtained by plating or vapor-depositing the above metal on a metal foil or a base material. In the case where the positive electrode collector 12 is made of a plurality of metal foils, the positive electrode collector 12 may have a certain layer between the plurality of metal foils. The thickness of the positive electrode collector 12 is not particularly limited. The thickness of the positive electrode current collector 12 may be, for example, 0.1 μm or more or 1 μm or more. The thickness of the positive electrode collector 12 may be 1mm or less or 100 μm or less.

1.2 electrolyte layer

The lithium-sulfur battery 100 has at least the 1 st electrolyte layer 21 and the 2 nd electrolyte layer 22 as the electrolyte layer 20. The electrolyte layer 20 is disposed between the positive electrode 10 and the negative electrode 30, and functions as a separator. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may optionally further contain a binder or the like.

1.2.1 electrolyte layer 1

The 1 st electrolyte layer 21 is disposed between the positive electrode 10 and the 2 nd electrolyte layer 22, and is in contact with the positive electrode 10. The positive electrode of the lithium-sulfur battery contains sulfur as a positive electrode active material as described above. Here, the volume change of sulfur associated with charge and discharge is large. According to the inventors' new findings, when the electrolyte layer in contact with the positive electrode is hard (for example, when the electrolyte layer in contact with the positive electrode is a sulfide solid electrolyte layer), cracks are likely to occur in the electrolyte layer due to expansion and shrinkage of sulfur associated with charge and discharge, and crack propagation is also likely to occur. If a crack is generated in the electrolyte layer, metallic lithium grows from the negative electrode side to the positive electrode side through the crack, and a short circuit is likely to occur. As a result, the chargeable/dischargeable capacity until the short circuit decreases. In contrast, the 1 st electrolyte layer 21 is in contact with the positive electrode 10 and contains a predetermined hydride solid electrolyte. According to the findings of the present inventors, the hydride solid electrolyte has flexibility and good formability. By disposing the 1 st electrolyte layer 21 containing the hydride solid electrolyte in contact with the positive electrode 10, even when sulfur contained in the positive electrode 10 expands and contracts in accordance with charge and discharge, stress generated by expansion and contraction is easily absorbed by the soft hydride solid electrolyte contained in the 1 st electrolyte layer 21, and cracking and propagation of cracking are hardly generated in the electrolyte layer 20. As a result, occurrence of short-circuiting caused by cracking of the electrolyte layer 20 as described above is suppressed. Further, it is considered that the chargeable/dischargeable capacity increases.

The hydride solid electrolyte has Li ions and complex ions containing H. The H-containing complex ion may also be represented by (M _m H _n ) ^α- And (3) representing. M in this case is an arbitrary positive number. n and α may take any positive numbers depending on M and the valence of the element M, etc. The element M is a nonmetallic element or a metallic element capable of forming complex ions. Alternatively, the element M may contain at least one of B, C and N as a nonmetallic element, or may contain B. In addition, for example, the element M may contain at least one of Al, ni, and Fe as a metal element. In particular, when the complex ion contains H and B or when the complex ion contains H, B and C, higher ion conductivity is easily ensured. Specific examples of the H-containing complex ion include (CB ₉ H ₁₀ )－－、(CB ₁₁ H ₁₂ )－－、(B ₁₀ H ₁₀ ) ^2- 、(B ₁₂ H ₁₂ ) ^2- 、(BH ₄ )－－、(NH ₂ )－－、(AlH ₄ ) -and combinations thereof. In particular in use (CB ₉ H ₁₀ )－－、(CB ₁₁ H ₁₂ ) Or combinations thereof, it is easy to ensure higher ionic conductivity.

Alternatively, the H-containing complex ion may be, for example, at least 1 selected from the following (A) to (C).

(A) Borane having a total charge of-2 and 6 to 12 boron atoms

(B) Carboranes with a total charge of-1 and having 1 carbon and 5 to 11 boron

(C) Carboranes having a total charge of-1 or-2 and having 2 carbon atoms and 4 to 10 boron atoms

In the case where the H-containing complex ion is the above-mentioned borane or carborane, a part of H in the borane or carborane may be substituted or unsubstituted. For example, 1 or more H of the H-containing complex ion may be substituted with at least 1 substituent selected from the following (X1) to (X3).

(X1) halogen

(X2) organic substituent

(X3) a combination of halogen and organic substituents

The H-containing complex ion may be an anion represented by any one of the following formulas (I) to (V).

Formula (I): [ B ] _y H _(y-z-i) R _z X _i ] ^2-

Formula (II): [ CB ] _(y-1) H _(y-z-i) R _z X _i ] ^-

Formula (III): [ C ₂ B _(y-2) H _(y-t-j-1) R _t X _j ] ^-

Formula (IV): [ C ₂ B _(y-3) H _(y-t-j) R _t X _j ] ^-

Formula (V): [ C ₂ B _(y-3) H _(y-t-j-1) R _t X _j ] ^2-

Wherein y is an integer of 6 to 12. (z+i) is an integer of 0 to y. (t+j) is an integer of 0 to (y-1). X is F, cl, br, I or a combination thereof. R in the formulae (I) to (V) may be any organic substituent or hydrogen.

In the above formulae (I) to (V), when I is an integer of 2 to y, or when j is an integer of 2 to (y-1), a plurality of halogen substituents are present in the complex ion. In this case, the plurality of halogen substituents may comprise F, cl, br, I or any combination thereof. For example, in a complex ion having 3 halogen substituents (i.e., when i or j is 3), the 3 halogen substituents may be 3 fluorine substituents; 1 chlorine substituent, 1 bromine substituent and 1 iodine substituent; or any other combination.

The H-containing complex ion may comprise a substituted or unsubstituted closo (closed) -boron cluster anion. For example, the H-containing complex ion may be selected from the group consisting of closo- [ B ₆ H ₆ ] ^2- 、closo-[B ₁₂ H ₁₂ ] ^2- 、closo-[CB ₁₁ H ₁₂ ] ^- And closo- [ C ₂ B ₁₀ H ₁₁ ] ^- And the like. The specific structure of the closo-boron cluster anion is disclosed in, for example, FIGS. 1A to 1C of Japanese patent application laid-open No. 2020-194777.

The content of the above-mentioned hydride solid electrolyte in the 1 st electrolyte layer 21 is not particularly limited. The 1 st electrolyte layer 21 may contain, for example, 50 mass% or more and 100 mass% or less, 60 mass% or more and 100 mass% or less, 70 mass% or more and 100 mass% or less, 80 mass% or more and 100 mass% or less, or 90 mass% or more and 100 mass% or less of the above-described hydride solid electrolyte.

The 1 st electrolyte layer 21 may contain an electrolyte other than the hydride solid electrolyte together with the hydride solid electrolyte. Examples of the electrolyte other than the hydride solid electrolyte include an electrolyte that can be contained in the positive electrode active material layer 11. However, the higher the proportion of the solid electrolyte contained in the 1 st electrolyte layer 21 as a whole, the more easily the 1 st electrolyte layer 21 can be softened. Moreover, the technical effects of the present disclosure are considered to be improved. In this regard, the proportion of the hydride solid electrolyte to the entire solid electrolyte contained in the 1 st electrolyte layer 21 is preferably 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, or 95% by mass or more and 100% by mass or less.

The binder that can be contained in the 1 st electrolyte layer 21 may be appropriately selected from, for example, binders exemplified as the binders that can be contained in the positive electrode active material layer 11. The binder contained in the 1 st electrolyte layer 21 and the binder contained in the positive electrode active material layer 11 may be of the same kind or of different kinds.

The shape of the 1 st electrolyte layer 21 is not particularly limited as long as it is disposed between the positive electrode 10 and the 2 nd electrolyte layer 22 and can be in contact with the positive electrode 10. The shape of the 1 st electrolyte layer 21 may be, for example, a sheet-like 1 st electrolyte layer 21 having a substantially planar surface. The thickness of the 1 st electrolyte layer 21 is not particularly limited. The thickness of the 1 st electrolyte layer 21 may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more. The thickness of the 1 st electrolyte layer 21 may be 2mm or less, 1mm or less, or 500 μm or less.

As shown in FIG. 2, the surface area A of the 1 st electrolyte layer 21 on the 2 nd electrolyte layer 22 side _E1 Can be greater than the surface area A of the positive electrode 10 on the side of the 1 st electrolyte layer 21 _P . That is, when the positive electrode 10 and the negative electrode 30 of the lithium-sulfur battery 100 are disposed on the upper side and the layers are viewed from above, the outer edge of the 1 st electrolyte layer 21 may be present on the positive side Outside the outer edge of the pole 10. For example, area A _P Relative to the area A _E1 Ratio A of _P /A _E1 May be 0.5 or more, 0.6 or more, or 0.7 or more. Area A _P Relative to the area A _E1 Ratio A of _P /A _E1 May be 1.0 or less, less than 1.0, 0.9 or less, or 0.8 or less. In addition, as shown in fig. 2, at least a part of the side surface of the positive electrode 10 may be covered with the 1 st electrolyte layer 21. More specifically, at least a portion of the positive electrode 10 side may be covered with the 1 st electrolyte layer 21 so that at least the positive electrode active material layer 11 in the positive electrode 10 is embedded in the 1 st electrolyte layer 21. Thus, it is considered that the area A passing through the 1 st electrolyte layer 21 _E1 Area A greater than the positive electrode 10 _P And/or at least a portion of the side surface of the positive electrode 10 is covered with the 1 st electrolyte layer 21, the stress from the positive electrode 10 can be more appropriately relaxed/absorbed by the 1 st electrolyte layer 21.

1.2.2 electrolyte layer 2

The 2 nd electrolyte layer 22 is disposed between the 1 st electrolyte layer 21 and the anode 30. The 2 nd electrolyte layer 22 contains an electrolyte different from the above-mentioned hydride solid electrolyte.

Examples of the electrolyte different from the hydride solid electrolyte include an electrolyte that can be contained in the positive electrode active material layer 11. Particularly, when the 2 nd electrolyte layer 22 contains an inorganic solid electrolyte, particularly a sulfide solid electrolyte, higher performance is easily exhibited. In addition, in the case where the sulfide solid electrolyte is contained in the 2 nd electrolyte layer 22, in the case where the sulfide solid electrolyte contains Li, P, and S, among them, in the case where Li, P, S, and halogen are contained, high performance is more easily exhibited. Examples of the sulfide solid electrolyte containing Li, P and S and containing Li, P, S and halogen include LiI-Li ₂ S-SiS ₂ 、LiI-Si ₂ S-P ₂ S ₅ 、Li ₂ S-P ₂ S ₅ -LiI-LiBr、LiI-Li ₂ S-P ₂ S ₅ 、LiI-Li ₂ S-P ₂ O ₅ 、LiI-Li ₃ PO ₄ -P ₂ S ₅ 、Li ₂ S-P ₂ S ₅ -GeS ₂ Etc. Wherein Li is ₂ S-P ₂ S ₅ The performance of LiI-LiBr is high.

The content of the electrolyte different from the hydride solid electrolyte in the 2 nd electrolyte layer 22 is not particularly limited. The 2 nd electrolyte layer 22 may contain, for example, 50 mass% or more and 100 mass% or less, 60 mass% or more and 100 mass% or less, 70 mass% or more and 100 mass% or less, 80 mass% or more and 100 mass% or less, or 90 mass% or more and 100 mass% or less of an electrolyte.

The 2 nd electrolyte layer 22 may contain a hydride solid electrolyte together with an electrolyte different from the hydride solid electrolyte. The proportion of the hydride solid electrolyte to the entire electrolyte contained in the 2 nd electrolyte layer 22 may be low. For example, the proportion of the hydride solid electrolyte in the entire electrolyte contained in the 2 nd electrolyte layer 22 may be 0% by mass or more and 50% by mass or less, 0% by mass or more and 40% by mass or less, 0% by mass or more and 30% by mass or less, 0% by mass or more and 20% by mass or less, 0% by mass or more and 10% by mass or less, or 0% by mass or more and 5% by mass or less.

The binder that can be contained in the 2 nd electrolyte layer 22 may be appropriately selected from, for example, binders exemplified as the binders that can be contained in the positive electrode active material layer 11. The binder contained in the 2 nd electrolyte layer 22 and the binder contained in the positive electrode active material layer 11 may be of the same kind or of different kinds. The binder contained in the 2 nd electrolyte layer 22 and the binder contained in the 1 st electrolyte layer 21 may be of the same kind or of different kinds.

The shape of the 2 nd electrolyte layer 22 is not particularly limited as long as it can be disposed between the 1 st electrolyte layer 21 and the anode 30. The shape of the 2 nd electrolyte layer 22 may be, for example, a sheet-like 2 nd electrolyte layer 22 having a substantially planar surface. The thickness of the 2 nd electrolyte layer 22 is not particularly limited. The thickness of the 2 nd electrolyte layer 22 may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more. The thickness of the 2 nd electrolyte layer 22 may be 2mm or less, 1mm or less, or 500 μm or less.

Surface area A of electrolyte layer 1 on the side of electrolyte layer 2 22 _E1 Surface area A of electrolyte layer 2 on the side of electrolyte layer 1, which can be in contact with electrolyte layer 2 _E2 The same or different. That is, when the positive electrode 10 and the negative electrode 30 of the lithium-sulfur battery 100 are disposed on the upper side and the respective layers are viewed from above, the outer edge positions of the 1 st electrolyte layer 21 and the 2 nd electrolyte layer 22 may or may not coincide.

1.2.3 other electrolyte layers

In fig. 1 and 2, as the electrolyte layer 20, only the 1 st electrolyte layer 21 and the 2 nd electrolyte layer 22 are explicitly shown. The lithium sulfur battery 100 may further have an electrolyte layer, not shown. For example, the lithium-sulfur battery 100 may have another electrolyte layer between the 1 st electrolyte layer 21 and the 2 nd electrolyte layer 22. For example, the lithium-sulfur battery 100 may have another electrolyte layer between the 2 nd electrolyte layer 22 and the negative electrode 30. The composition and thickness of the other electrolyte layer are not particularly limited. From the viewpoint of simplifying the battery structure, the lithium-sulfur battery 100 may be provided with only the 1 st electrolyte layer 21 and the 2 nd electrolyte layer 22 as the electrolyte layer 20. Specifically, the 1 st electrolyte layer 21 may be disposed between the positive electrode 10 and the 2 nd electrolyte layer 22, and one surface of the 1 st electrolyte layer 21 is in contact with the positive electrode 10 and the other surface is in contact with the 2 nd electrolyte layer 22. The 2 nd electrolyte layer 22 may be disposed between the 1 st electrolyte layer 21 and the anode 30, and one face of the 2 nd electrolyte layer 22 is in contact with the 1 st electrolyte layer 21 and the other face is in contact with the anode 30.

1.3 negative electrode

The negative electrode 30 may function properly as a negative electrode of a lithium-sulfur battery. The structure thereof is not particularly limited. As shown in fig. 1, the anode 30 may include an anode active material layer 31 and an anode current collector 32.

1.3.1 negative electrode active material layer

The anode active material layer 31 contains at least an anode active material, and may optionally contain an electrolyte, a conductive auxiliary agent, a binder, and the like. The anode active material layer 31 may further contain other various additives. The content of each component in the anode active material layer 31 may be appropriately determined according to the target battery performance. For example, the content of the anode active material may be 60 mass% or more, 70 mass% or more, 80 mass% or more, or 90 mass% or more, and 100 mass% or less, based on 100 mass% of the entire anode active material layer 31 (entire solid component). The shape of the anode active material layer 31 is not particularly limited. The negative electrode active material layer 31 may be, for example, a sheet-like negative electrode active material layer having a substantially planar shape. The thickness of the anode active material layer 31 is not particularly limited. The thickness of the anode active material layer 31 may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more. The thickness of the anode active material layer 31 may be 2mm or less, 1mm or less, or 500 μm or less.

As the negative electrode active material, lithium is used, for example. Lithium may be used as the negative electrode active material. The lithium may be metallic lithium, may be a lithium alloy, or may be a lithium compound. The negative electrode active material layer 31 may contain a negative electrode active material other than lithium. Examples of the negative electrode active material other than lithium include Si, si alloy, si compound, and other Si-based active materials, and graphite and other carbon-based active materials. In addition, when lithium is used as the negative electrode active material, the problems of lithium growth through cracks in the electrolyte layer and short-circuiting caused by lithium growth are particularly likely to occur. In contrast, in the lithium-sulfur battery 100, as described above, the predetermined hydride solid electrolyte is contained in the 1 st electrolyte layer 21, so that cracking of the electrolyte layer is easily suppressed, and occurrence of short-circuiting due to lithium growth is easily suppressed. In this regard, in the lithium-sulfur battery 100, the proportion of lithium in the entire negative electrode active material contained in the negative electrode active material layer 31 may be high. Specifically, the proportion of lithium in the entire negative electrode active material contained in the negative electrode active material layer 31 may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or more and 90% by mass or less and 100% by mass or less.

The shape of the negative electrode active material may be any general shape as long as it is a negative electrode active material of a lithium-sulfur battery. The negative electrode active material may be, for example, sheet-like or granular. The negative electrode active material may be accompanied by precipitation of lithium during charging or may be accompanied by dissolution of lithium during discharging. In this case, the anode active material layer 31 may be a layer composed of metallic lithium or a lithium alloy (for example, metallic lithium foil or lithium alloy foil).

The electrolyte, the conductive additive, and the binder that can be contained in the negative electrode active material layer 31 can be appropriately selected from the materials exemplified as the materials that can be contained in the positive electrode active material layer 11. The electrolyte, the conductive additive, and the binder contained in the negative electrode active material layer 31 may be the same type as or different from the electrolyte, the conductive additive, and the binder contained in the positive electrode active material layer 11.

1.3.2 negative electrode collector

As shown in fig. 1, the negative electrode 30 may include a negative electrode current collector 32 in contact with the negative electrode active material layer 31. As the negative electrode current collector 32, any current collector commonly used as a negative electrode current collector of a lithium-sulfur battery can be used. The negative electrode current collector 32 may be foil-shaped, plate-shaped, mesh-shaped, perforated metal-shaped, foam, or the like. The negative electrode current collector 32 may be formed of a metal foil or a metal mesh, or may be formed of a carbon sheet. Particularly, the metal foil and the carbon sheet are excellent in handleability and the like. The negative electrode current collector 32 may be composed of a plurality of metal foils or carbon sheets. As a metal constituting the negative electrode current collector 32, cu, ni, cr, au, pt, ag, al, fe, ti, zn, co, stainless steel, and the like are exemplified. In particular, from the viewpoint of ensuring reduction resistance, the viewpoint of being less likely to alloy with lithium, and the like, the negative electrode current collector 32 may contain at least 1 metal selected from Cu, ni, and stainless steel, or may be composed of a carbon sheet. The negative electrode current collector 32 may have some coating on its surface for the purpose of adjusting resistance or the like. In the case where the negative electrode current collector 32 is composed of a plurality of metal foils or a plurality of carbon sheets, the negative electrode current collector 32 may have a layer between the plurality of metal foils or the plurality of carbon sheets. The thickness of the negative electrode current collector 32 is not particularly limited. The thickness of the negative electrode current collector 32 may be, for example, 0.1 μm or more and 1 μm or more, and may be 1mm or less and 100 μm or less.

1.4 other structures

The lithium-sulfur battery 100 may have at least the above-described respective structures. The lithium-sulfur battery 100 may have other structures than those described above. The structure described below is an example of other structures that the lithium-sulfur battery 100 may have.

1.4.1 outer package

The lithium-sulfur battery 100 may be a battery in which the above-described structures are housed in an exterior body. More specifically, a portion other than a connector, a terminal, or the like for taking out electric power from the lithium-sulfur battery 100 to the outside may be housed inside the exterior body. The exterior body may be any of those known as an exterior body of a battery. For example, a laminate film may be used as the exterior body. In addition, a plurality of lithium sulfur batteries 100 may be electrically connected or may be stacked arbitrarily to form a battery pack. In this case, the battery pack may be housed in a known battery case.

1.4.2 sealing resin

In the lithium-sulfur battery 100, each of the above structures may be sealed with a resin. For example, at least the side surface (surface along the lamination direction) of the laminate composed of the layers may be sealed with a resin. This makes it easy to suppress the mixing of water into the layers. As the sealing resin, a known thermosetting resin or thermoplastic resin can be used.

1.4.3 restraining Member

The lithium-sulfur battery 100 may also have a constraining member for constraining the layers in the stacking direction. By applying a constraint pressure to each layer in the stacking direction by the constraint member, the internal resistance of each layer is easily reduced. The constraint pressure in this case may be, for example, 50MPa or less, 30MPa or less, or 10MPa or less. The constraint pressure in this case may be 0.1MPa or more or 1.0MPa or more.

1.4.4 cell shape etc

The lithium-sulfur battery 100 may have other obvious structures such as necessary terminals. Examples of the shape of the lithium-sulfur battery 100 include button type, laminate type, cylindrical type, square type, and the like. In particular, the laminated type has high performance.

2. Method for manufacturing lithium-sulfur battery

The lithium sulfur battery 100 may be manufactured as follows. That is, as shown in fig. 3A to 3E, the method of manufacturing the lithium-sulfur battery 100 according to an embodiment may include:

step S1: a 1 st transfer material 51 is obtained by forming a 1 st electrolyte layer 21 on the surface of the base material 41;

step S2: forming the 2 nd electrolyte layer 22 on the surface of the base material 42 to obtain a 2 nd transfer material 52;

step S3: applying a pressure P in a lamination direction after laminating the 1 st transfer material 51 and the positive electrode 10 ₁ Transferring the 1 st electrolyte layer 21 to the surface of the positive electrode 10 to obtain a 1 st laminate 61 of the positive electrode 10 and the 1 st electrolyte layer 21;

Step S4: applying a pressure P in a lamination direction after laminating the 2 nd transfer material 52 and the 1 st laminate 61 ₂ Transferring the 2 nd electrolyte layer 22 onto the surface of the 1 st electrolyte layer 21 of the 1 st laminate 61 to obtain a 2 nd laminate 62 of the positive electrode 10, the 1 st electrolyte layer 21, and the 2 nd electrolyte layer 22; and

step S5: after the 2 nd laminate 62 and the anode 30 are laminated, a pressure P is applied in the lamination direction ₃ Thus, a lithium-sulfur battery 100 having the positive electrode 10, the 1 st electrolyte layer 21, the 2 nd electrolyte layer 22, and the negative electrode 30 in this order was obtained.

The step S2 may be performed before the step S1. The step S2 may be performed between the steps S1 and S3. The step S2 may be performed after the step S3.

2.1 Process S1

As shown in fig. 3A, in step S1, the 1 st electrolyte layer 21 is formed on the surface of the base material 41, and the 1 st transfer material 51 is obtained.

The base material 41 is subjected to the pressure P in the step S3 described later ₁ And then can be peeled from the 1 st electrolyte layer 21. For example, a metal foil, a resin film, or the like can be used as the base material 41.

In step S1, the method of forming the 1 st electrolyte layer 21 on the surface of the base material 41 is not particularly limited. For example, the 1 st transfer material 51 may be obtained by applying a slurry containing a material constituting the 1 st electrolyte layer 21 to the surface of the base material 41 and then drying the applied slurry. Alternatively, the 1 st transfer material 51 may be obtained by dry-molding the material constituting the 1 st electrolyte layer 21 together with the base material 41.

2.2 Process S2

As shown in fig. 3B, in step S2, the 2 nd electrolyte layer 22 is formed on the surface of the base material 42, and the 2 nd transfer material 52 is obtained.

The base material 42 is subjected to the pressure P in the step S4 to be described later ₂ And can be peeled from the 2 nd electrolyte layer 22. For example, a metal foil, a resin film, or the like can be used as the base material 42.

In step S2, the method of forming the 2 nd electrolyte layer 22 on the surface of the base material 42 is not particularly limited. For example, the slurry containing the material constituting the 2 nd electrolyte layer 22 may be applied to the surface of the base material 42, and then dried, thereby obtaining the 2 nd transfer material 52. Alternatively, the 2 nd transfer material 52 may be obtained by dry-molding the material constituting the 2 nd electrolyte layer 22 together with the base material 42.

2.3 Process S3

As shown in fig. 3C, in step S3, after the 1 st transfer material 51 and the positive electrode 10 are laminated, a pressure P is applied in the lamination direction ₁ The 1 st electrolyte layer 21 is transferred to the surface of the positive electrode 10. Then, the 1 st laminate 61 of the positive electrode 10 and the 1 st electrolyte layer 21 is obtained.

As described above, the positive electrode 10 may have the positive electrode active material layer 11 and the positive electrode current collector 12. In this case, for example, a slurry containing a material constituting the positive electrode active material layer 11 may be applied to the surface of the positive electrode current collector 12, and then dried, thereby obtaining the positive electrode 10. Alternatively, the positive electrode 10 may be obtained by dry-molding the material constituting the positive electrode active material layer 11 together with the positive electrode current collector 12.

In step S3, for example, the 1 st electrolyte layer 21 of the 1 st transfer material 51 and the positive electrode active material layer 11 of the positive electrode 10 are laminated in a superimposed manner, and a pressure P is applied in the lamination direction ₁ The 1 st electrolyte layer 21 is tightly bonded to the interface of the positive electrode active material layer 11. Pressure P ₁ Can be a 1 st electrolyte layer 21, and the pressure at which the solid electrolyte of the hydride contained therein is plastically deformed. Specifically, the pressure P ₁ May be 100MPa or more, 200MPa or more, or 300MPa or more. Pressure P ₁ The upper limit of (2) is not particularly limited. Pressure P ₁ The pressure is sufficient to prevent the layers from being broken. The pressurizing method in step S3 is not particularly limited. As the pressurizing method in step S3, various pressurizing methods such as CIP, HIP, roll pressing, uniaxial pressing, and die pressing can be used.

In step S3 and steps S4 and S5 described later, the term "applying pressure in the lamination direction" means applying pressure at least in the lamination direction, and may include applying pressure in a direction other than the lamination direction together with applying pressure in the lamination direction.

In step S3, as described above, after the 1 st transfer material 51 and the positive electrode 10 are laminated and pressurized, the base material 41 is removed by peeling the base material 41 or the like from the 1 st transfer material 51, whereby the 1 st laminated body 61 of the positive electrode 10 and the 1 st electrolyte layer 21 can be obtained.

2.4 Process S4

As shown in fig. 3D, in step S4, the 2 nd transfer material 52 is laminated with the 1 st laminate 61, and then a pressure P is applied in the lamination direction ₂ The 2 nd electrolyte layer 22 is transferred onto the surface of the 1 st electrolyte layer 21 of the 1 st laminate 61 to obtain a 2 nd laminate 62 of the positive electrode 10, the 1 st electrolyte layer 21, and the 2 nd electrolyte layer 22.

In step S4, for example, the 2 nd electrolyte layer 22 of the 2 nd transfer material 52 is laminated on the 1 st electrolyte layer 21 of the 1 st laminate 61, and a pressure P is applied in the lamination direction ₂ The interface between the 1 st electrolyte layer 21 and the 2 nd electrolyte layer 22 is tightly bonded. Pressure P ₂ The pressure at which the electrolyte contained in the 2 nd electrolyte layer 22 can be plastically deformed may be used. Specifically, the pressure P ₂ May be 100MPa or more, 200MPa or more, or 300MPa or more. Pressure P ₂ The upper limit of (2) is not particularly limited. Pressure P ₂ The pressure is sufficient to prevent the layers from being broken. The pressurizing method in step S4 is not particularly limited. The pressurizing method in step S4 may be CIP, HIP, roll, uniaxial pressing, or die pressingVarious pressurizing methods such as pressing.

In step S4, as described above, after the 2 nd transfer material 52 and the 1 st laminate 61 are laminated and pressurized, the base material 42 is removed by peeling the base material 42 or the like from the 2 nd transfer material 52, whereby the 2 nd laminate 62 of the positive electrode 10, the 1 st electrolyte layer 21, and the 2 nd electrolyte layer 22 can be obtained.

2.5 Process S5

As shown in fig. 3E, in step S5, after the 2 nd laminate 62 is laminated with the anode 30, a pressure P is applied in the lamination direction ₃ Thus, a lithium-sulfur battery 100 having the positive electrode 10, the 1 st electrolyte layer 21, the 2 nd electrolyte layer 22, and the negative electrode 30 in this order was obtained.

As described above, the anode 30 may have the anode active material layer 31 and the anode current collector 32. In this case, for example, a slurry containing a material constituting the anode active material layer 31 may be applied to the surface of the anode current collector 32, and then dried, thereby obtaining the anode 30. Alternatively, the negative electrode 30 may be obtained by dry-molding the material constituting the negative electrode active material layer 31 together with the negative electrode current collector 32. Alternatively, a metal lithium foil or a lithium alloy foil as the anode active material layer 31 may be attached to the surface of the anode current collector 32, thereby obtaining the anode 30.

In step S5, for example, the 2 nd electrolyte layer 22 of the 2 nd laminate 62 is laminated on the anode active material layer 31 of the anode 30, and a pressure P is applied in the lamination direction ₃ The interface between the 2 nd electrolyte layer 22 and the anode active material layer 31 is tightly bonded. Pressure P ₃ There is no particular limitation. Pressure P ₃ For example, may be less than 100MPa. Pressure P ₃ The lower limit of (2) is not particularly limited. Pressure P ₃ The pressure may be such that the desired interfacial adhesion can be obtained. The pressurizing method in step S5 is not particularly limited. As the pressurizing method in step S5, various pressurizing methods such as CIP, HIP, roll pressing, uniaxial pressing, and die pressing can be used.

The lithium-sulfur battery 100 manufactured as described above may be mounted with terminals or the like as necessary, and then housed in an exterior body or the like, for example.

3. Vehicle with lithium-sulfur battery

As described above, the lithium sulfur battery of the present disclosure has a high capacity. Such a battery may be suitably used in at least one vehicle selected from, for example, a Hybrid Electric Vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and an electric vehicle (BEV). That is, the techniques of the present disclosure also have the following aspects: a vehicle having a lithium sulfur battery with a positive electrode, a 1 st electrolyte layer, a 2 nd electrolyte layer, and a negative electrode, the 1 st electrolyte layer being disposed between the positive electrode and the 2 nd electrolyte layer and in contact with the positive electrode, the 2 nd electrolyte layer being disposed between the 1 st electrolyte layer and the negative electrode, the 1 st electrolyte layer containing a hydride solid electrolyte having Li ions and H-containing complex ions, the 2 nd electrolyte layer containing an electrolyte different from the hydride solid electrolyte.

Hereinafter, the technology of the present disclosure will be described in more detail with reference to examples. However, the technology of the present disclosure is not limited to the following examples.

1. Example 1

1.1 preparation of Positive electrode mixture

As a starting material constituting the positive electrode mixture, 1.05g of elemental sulfur (S) and 0.852g of P were used ₂ S ₅ And 0.57g of VGCF, the starting materials are compounded by mechanical milling. Specifically, the starting materials were weighed in a glove box having a dew point temperature of-70 ℃ or lower, and kneaded in an agate mortar for 15 minutes. A tank (45 mL, zrO ₂ Prepared) and zirconia ballsAbout 96g, about 500) of the above-mentioned materials, the kneaded powder was placed in a pot together with zirconia balls, and the operations of mechanically grinding at 500rpm for 1 hour, stopping for 15 minutes, and mechanically grinding at 500rpm for 1 hour and stopping for 15 minutes were repeated for 48 hours, thereby obtaining a positive electrode mixture.

1.2 preparation of Positive electrode

Adding a mesitylene solution containing 5 mass% SBR and mesitylene into a polypropylene container, usingThe shaker was mixed for 3 minutes. Adding a positive electrode mixture (S) ₈ -P ₂ S ₅ after/C), the mixing operation with a shaker for 3 minutes and the mixing operation with an ultrasonic dispersing device for 30 seconds were repeated 2 times, respectively. Next, the positive electrode mixture slurry obtained immediately after mixing for 5 seconds by an ultrasonic dispersion device was applied to an Al foil as a positive electrode current collector using a doctor blade having a coating gap of 350 μm. After the surface of the coated positive electrode mixture was visually confirmed to be dried, the positive electrode was dried on a heating plate at 100 ℃ for 30 minutes, thereby obtaining a positive electrode having a positive electrode active material layer and a positive electrode current collector. The obtained positive electrode is blanked into But is used.

1.3 production of transfer Material 1

A heptane solution containing 5 wt% of ABR, heptane and butyl butyrate were put into a polypropylene container, and mixed for 3 minutes by a shaker. To which a hydride solid electrolyte [ [ LiCB ] is added ₉ H ₁₀ ] _0.7 [LiCB ₁₁ H ₁₂ ] _0.3 、D ₅₀ ＝2μm]After that, the mixing operation with a shaker for 3 minutes and the mixing operation with an ultrasonic dispersing device for 30 seconds were repeated 2 times, respectively. Next, the 1 st electrolyte paste obtained immediately after mixing for 5 seconds by an ultrasonic dispersion device was applied to an Al foil as a base material using an applicator having a coating gap of 500 μm. After the surface of the applied electrolyte was visually confirmed to be dried, it was dried on a heating plate at 165 ℃ for 30 minutes, thereby obtaining a 1 st transfer material composed of a base material and a 1 st electrolyte layer. The ABR amount contained in the 1 st electrolyte layer was 10 wt%. The 1 st transfer material is punched intoBut is used.

1.4 production of the 2 nd transfer Material

A heptane solution containing 5 wt% of ABR, heptane and butyl butyrate were put into a polypropylene container, and mixed for 3 minutes by a shaker. To which a sulfide solid electrolyte (Li ₂ S-P ₂ S ₅ -LiI-LiBr based solid electrolyte, D ₅₀ =0.5 μm), the mixing with a shaker for 3 minutes and the mixing with an ultrasonic dispersion apparatus for 30 seconds were repeated 2 times, respectively. Next, the 2 nd electrolyte paste obtained immediately after mixing for 5 seconds by an ultrasonic dispersion apparatus was applied to an Al foil as a base material using an applicator having a coating gap of 350 μm. After the surface of the applied electrolyte was visually confirmed to be dried, it was dried on a heating plate at 165 ℃ for 30 minutes, thereby obtaining a 2 nd transfer material composed of a base material and a 2 nd electrolyte layer. The ABR amount contained in the 2 nd electrolyte layer was 10 wt%. The obtained 2 nd transfer material is blanked into But is used.

1.5 preparation of negative electrode

A negative electrode was produced by attaching a metal lithium foil (thickness 70 μm) to the surface of a carbon sheet as a negative electrode current collector. The obtained negative electrode is punched intoBut is used.

1.6 manufacturing of lithium Sulfur Battery

The positive electrode and the 1 st transfer material were stacked, and the base material was peeled off after pressing at a pressure of 392MPa, whereby the 1 st electrolyte layer was transferred onto the surface of the positive electrode active material layer, to obtain a 1 st laminate of the positive electrode and the 1 st electrolyte layer.

Next, the 1 st laminate and the 2 nd transfer material were stacked, and the base material was peeled off after pressing at a pressure of 392MPa, whereby the 2 nd electrolyte layer was transferred onto the surface of the 1 st electrolyte layer of the 1 st laminate, to obtain a 2 nd laminate of the positive electrode, the 1 st electrolyte layer, and the 2 nd electrolyte layer.

Next, the 2 nd laminate and the negative electrode were stacked and temporarily pressed, and then pressed by Cold Isostatic Pressing (CIP) at a pressure of 98MPa, thereby obtaining a lithium-sulfur battery having a positive electrode, a 1 st electrolyte layer, a 2 nd electrolyte layer, and a negative electrode in this order. The resulting cell was sealed into a laminate and then restrained at 10 MPa.

2. Example 2

Except for using blankingA lithium-sulfur battery was fabricated in the same manner as in example 1, except for the positive electrode.

3. Comparative example 1

A lithium-sulfur battery was fabricated in the same manner as in example 2, except that the 2 nd transfer material was used instead of the 1 st transfer material (i.e., a lithium-sulfur battery having a positive electrode, a 2 nd electrolyte layer, and a negative electrode in this order was fabricated).

4. Comparative example 2

A lithium-sulfur battery was produced in the same manner as in example 2, except that the 1 st transfer material and the 2 nd transfer material were replaced (i.e., a lithium-sulfur battery having a positive electrode, a 2 nd electrolyte layer, a 1 st electrolyte layer, and a negative electrode in this order was produced).

5. Comparative example 3

A lithium-sulfur battery was fabricated in the same manner as in example 2, except that the 1 st transfer material was used instead of the 2 nd transfer material (i.e., a lithium-sulfur battery having, in order, a positive electrode, a 1 st electrolyte layer, and a negative electrode was fabricated).

6. Electrochemical assay

The batteries of examples and comparative examples were each soaked in a constant temperature bath at 60℃for 3 hours, and then discharged and charged at a current density of 0.46mA (corresponding to 0.05C) at the following capacity levels. The 10 minutes was discontinued between the grades. The cut-off voltage is 1.5-3.1V. The maximum charge capacity up to the short circuit was measured for each of the batteries of examples and comparative examples. Based on the maximum charge capacity, a "battery capacity" per 1g of the positive electrode mixture was determined.

Class 1: up to 0.1mAh, grade 2: up to 0.5mAh, grade 3: up to 1.0mAh, grade 4: up to 2.0mAh, grade 5: up to 3.0mAh, grade 6: up to 3.5mAh, grade 7: up to 4.0mAh, grade 8: up to 5.0mAh, grade 9: up to 6.0mAh, grade 10: up to 7.0mAh, grade 11: up to 8.0mAh

7. Evaluation results

Table 1 below shows the area ratio of the positive electrode to the electrolyte layer, the structure of the electrolyte layer, and the battery capacity for each of the examples and comparative examples.

TABLE 1

The following are apparent from the results shown in Table 1.

(1) In the case where only the sulfide solid electrolyte layer was used as the electrolyte layer (comparative example 1), the charge capacity obtained until short-circuiting was small. It is considered that cracks are generated in the entire electrolyte layer due to expansion of sulfur as a positive electrode active material during discharge, and lithium grows through the cracks during charge, thereby generating a short circuit at a low capacity.

(2) In the case where the sulfide solid electrolyte layer and the hydride solid electrolyte layer are formed as the electrolyte layer, and the sulfide solid electrolyte layer is formed on the positive electrode side and the hydride solid electrolyte layer is formed on the negative electrode side (comparative example 2), the charge capacity obtained until short-circuiting is slightly improved as compared with comparative example 1. In comparative example 2, it is considered that cracks were generated in the sulfide solid electrolyte layer due to expansion of sulfur as the positive electrode active material at the time of discharge, and further, a part of the cracks were propagated to the hydride solid electrolyte layer. That is, the amount of cracks may be slightly smaller than that of comparative example 1. Thus, the capacity up to the short circuit is considered to be slightly increased.

(3) In the case where only the hydride solid electrolyte layer was used as the electrolyte layer (comparative example 3), the charge capacity obtained until the short circuit was further improved as compared with comparative examples 1 and 2. In comparative example 3, even if sulfur, which is a positive electrode active material, expands during discharge, stress is generated in the electrolyte layer, and this stress is absorbed by the soft hydride solid electrolyte layer, and cracking is unlikely to occur. Thus, the capacity up to the short circuit is considered to be improved. However, since each performance such as ion conductivity of the hydride solid electrolyte layer is lower than that of the sulfide solid electrolyte, it is difficult to obtain a sufficient battery capacity.

(4) When the sulfide solid electrolyte layer and the hydride solid electrolyte layer were formed as the electrolyte layer, and the hydride solid electrolyte layer was disposed on the positive electrode side and the sulfide solid electrolyte layer was disposed on the negative electrode side (examples 1 and 2), the charge capacity obtained by the short circuit was further improved as compared with comparative example 3. In examples 1 and 2, even if sulfur as the positive electrode active material expands and stress is generated in the electrolyte layer during discharge, the stress is absorbed by the soft hydride solid electrolyte layer, and cracking is unlikely to occur. Thus, the capacity up to the short circuit is considered to be improved. In addition, it is considered that the battery capacity is further improved by disposing sulfide solid electrolyte excellent in various performances such as ion conductivity on the negative electrode side.

In the above-described embodiment, the case where only a specific hydride solid electrolyte is used as the electrolyte in the 1 st electrolyte layer and only a specific sulfide solid electrolyte is used as the electrolyte in the 2 nd electrolyte layer is exemplified. However, the technology of the present disclosure is not limited to this embodiment. For example, even when an electrolyte other than a hydride solid electrolyte or a sulfide solid electrolyte is used in the 2 nd electrolyte layer, the high effect of the technique of the present disclosure can be expected. In addition, the 1 st electrolyte layer or the 2 nd electrolyte layer may contain a certain electrolyte.

In the above examples, the case where only elemental sulfur was used as the positive electrode active material and only metallic lithium was used as the negative electrode active material was exemplified. However, the technology of the present disclosure is not limited to this embodiment. Even in the case of a sulfur-based positive electrode active material other than elemental sulfur, the same problems as in the case of elemental sulfur occur due to the volume change during charge and discharge, and this problem can be solved by the technology of the present disclosure. The negative electrode active material may be any material that can supply lithium to the sulfur-based positive electrode active material during discharge. That is, it is considered that the technology of the present disclosure can be widely applied to lithium-sulfur batteries that employ a sulfur-based active material as a positive electrode active material and lithium ions as carrier ions.

As described above, according to the lithium-sulfur battery having the following configuration, the charge capacity up to the short circuit can be improved. That is, it can be said that a lithium-sulfur battery having the following configuration has a high charge-discharge capacity.

(1) The lithium sulfur battery has a positive electrode, a 1 st electrolyte layer, a 2 nd electrolyte layer, and a negative electrode.

(2) The 1 st electrolyte layer is disposed between the positive electrode and the 2 nd electrolyte layer, and is in contact with the positive electrode.

(3) The 2 nd electrolyte layer is disposed between the 1 st electrolyte layer and the negative electrode.

(4) The 1 st electrolyte layer contains a hydride solid electrolyte. The hydride solid electrolyte has Li ions and H-containing complex ions.

(5) The 2 nd electrolyte layer contains an electrolyte different from the hydride solid electrolyte.

Claims

1. A lithium sulfur battery comprising:

a positive electrode,

An electrolyte layer 1,

2 nd electrolyte layer

A negative electrode,

2. The lithium sulfur battery of claim 1, the complex ion comprising hydrogen, boron, and carbon.

3. The lithium sulfur battery according to claim 1, a surface area of the 1 st electrolyte layer on the 2 nd electrolyte layer side is larger than a surface area of the positive electrode on the 1 st electrolyte layer side.

4. A lithium sulfur battery according to claim 3, at least a part of a side face of the positive electrode is covered with the 1 st electrolyte layer.

5. The lithium sulfur battery of any one of claims 1-4, the 2 nd electrolyte layer comprising a sulfide solid electrolyte.

6. The lithium sulfur battery of claim 5, the sulfide solid electrolyte comprising lithium, phosphorus, sulfur, and halogen.